Thomson was suspended for one week in the wake of the All Blacks' 51-22 victory over Scotland earlier this month. The blindside flanker was yellow carded during the game for his challenge on Scotland's Alasdair Strokosch but was also later cited and called to appear before an independent disciplinary panel.

Judicial officer Jean Noel Couraud upheld the citing complaint but viewed the offence to be at the lower end of the IRB's scale. That level of sanction demands a two-week ban but Couraud allowed one week of mitigation, "taking into account, in particular, the player's (Thomson's) conduct at the hearing."

The ruling provoked widespread anger with former England hooker Brian Moore describing it as "ludicrously lenient". IRB chief executive Brett Gosper repsonded to the criticism by saying that he would review the case that fell under the jurisdiction of the Six Nations Committee.

Having completed that review, they have issued a strongly-worded statement declaring their intention to appeal the ban in order to protect the image of the game.

"As custodians of Rugby worldwide, the IRB has a duty to protect its image, values and integrity together with the welfare of players at all levels in order that the sport can continue its unprecedented growth and welcome more men, women and children to the Rugby family," the statement said.

"At the very heart of this mission is the universal application of the disciplinary process as set out in Regulation 17. This IRB Disciplinary regulation is intended to protect all players and the Game through the strict application of a sanctioning regime that acts as a strong deterrent against acts of foul play.

"This stance was reaffirmed by leading international players, coaches, referees and administrators attending the IRB Morality Conference in London in March this year who unanimously agreed that a tough and consistent stance on discipline is key to Rugby's integrity.

"After careful consideration and having reviewed the full written decision in the Thomson case well within the permitted 72 hours of receipt, the IRB strongly believes that the sanction of one week is unduly lenient for this particular act of foul play and not aligned with the sanctions handed down in similar cases.

"The IRB firmly believes it is in the best interests of the Game and its integrity to exercise its ability to appeal the Thomson decision. The right of appeal by the IRB (in defined circumstances) and for Host Unions and tournament organisers was introduced into the revised Regulation 17 effective on June 1 this year to uphold the integrity of the disciplinary process in appropriate cases."

Thomson missed the All Blacks' victory over Italy last weekend but it currently available for their clash with Wales this weekend and the game against England on December 1. The IRB said arrangements for an appeal hearing will be announced shortly.

In a separate development, the Six Nations Committee announced tonight that Australia forward Rob Simmons has appealed his eight-week suspension imposed for a dangerous tip tackle on France flanker Yannick Nyanga.

Simmons was found guilty of the offence at a disciplinary hearing last week after being cited. The incident happened during Australia's 33-6 loss to Les Bleus in Paris on November 10. The appeal will be heard by a three-man, IRB-appointed committee, with a date to be announced.